Rock drills



Oct. 18, 1955 F. BROWN-COOMBES ROCK DRILLS 3 Sheets-Sheet 1 Filed Dec, 15, 1951 Q Qm Oct. 18, 1955 F. BRowN-cooMBEs ROCK DRILLS 3 Sheets-Sheet 2 Filed Dec. 15, 1951 NM @NW. mwq

SRN N WW Attorney Oct 1955 F. BROWN-COOMBES 2,721,057

ROCK DRILLS Filed Dec. 15, 1951 3 Sheets-Sheet 3 F156 5.; MfiW-M [WWW Attorney United States Patent ROCK DRILLS Frank Brown-Coombes, Fraddam, Hayle, England, assignor to Holman Brothers Limited, Camborne, England, a British company Application December 15, 1951, Serial No. 261,869

15 Claims. (Cl. 25547) This invention relates to rock drills of the kind using rotary bits and has for its object the provision of improved rock drills of this kind.

According to the invention there is provided a rock drill comprising a body portion adapted to be secured to a supporting stand or the like, a compressed air motor, a drill bit supporting member adapted to be rotated by drive from said motor and arranged for longitudinal movement relative to said body portion, a piston, longitudinal movement of which produces corresponding movement of said drill bit supporting member, and a closed circuit hydraulic system including a pump driven by said motor and adapted to supply liquid under pressure to one or the other side of said piston for producing longitudinal movement thereof.

One construction of rock drill in accordance with the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 is a cross sectional view through the drill along the line l-l in Figure 2a, while 2a and 2b, when joined end-to-end with Figure 2a, at the left constitute an opened-out side view along the line I -li in Figure 1, and

Figure 3 is a diagrammatic representation of the feed control system used on the drill.

As shown in Figures 1, 2a and 2b of the drawings, the drill comprises a main casing or body portion which is formed with four parallel bores. The largest bore 11 is disposed in the lower part of the casing 10, its forward part accommodating a cylindrical pneumatic motor 12 for rotating the drill bit. The rear part of this bore 11 accommodates a hydraulic unit comprising pump 13, reservoir 14 and control block indicated generally at 15, for effecting the feed of the drill bit. The upper bore 16 accommodates the hydraulic feed cylinder 16a, in which works a tubular arm 17. Between and to opposite sides of these two bores 11 and 16 are two smaller bores 18 and 19, bore 18 containing a hollow shaft 20 which is supported in suitable bearings. The shaft 2% is driven through gears 21 from the pneumatic motor 12 and at its rear end drives the pump 13 of the hydraulic unit through gears 22. The bore 19 accommodates a torque resistor tube 9.

Considering now the construction in more detail the pneumatic motor 12 receives compressed air from an external source through the inlet 23 to which an airline is connected. The supply of air to the motor 12 is controlled by means of the rotatable sleeve 24 having an aperture 25 which can be aligned with the inlet 23, rotation of the sleeve 24 being efiected by means of the handle 26. The supply of air is regulated automatically by a slide valve 27a disposed within sleeve 24 and operated by a centrifugal governor 27 on the shaft of motor 12, which is of conventional type. From valve 27a the air flows through passage 27b to motor 12.

The shaft 20, to which drive from the motor 12 is transmitted through the gears 21, is supported in bearings 28, 29 fixed in the end covers 30, 31 respectively.

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In addition to driving the pump 13 the shaft 20 imparts rotary motion to a shaft 32 which is slidable Within the shaft 20. Shaft 20 is keyed to shaft 32 by a key 3212 rigid with shaft 20 which slides in a groove 32a in shaft 32.

The ram 17 slides on an inner tube 33 which together with an outer tube 34 forms a ram cylinder within which slides the piston 35 fixed to one end of the ram 17. The ends of the cylinder are closed by an end plate 36 and a ram guide 37 which latter is fixed to the main casing 19. Suitable sealing rings 38 are fitted to the piston 35 and the ram guide 37 to restrict oil leakage. The ends of the ram cylinder communicate with openings 39 and 40 which are connected by oil pipe lines 41 and 42 respectively to the control block 15. By operation of the control block 15 in the manner to be described hereafter pressure oil can be admited to either one or the other end of the ram cylinder to move the ram 17 in a desired direction. Mounted on the front end of the ram 17 and the torque resistor tube 9 is a gear box 43 carrying a hollow spindle 44 which is adapted to support a drill chuck or adaptor (not shown). The spindle 44 is driven from the slidable shaft 32 through gears 45, 46. The torque resistor tube 9 serves together with the sliding shaft 32 as a support for the gear box 43 to which it is secured and is slidable in bore 19. The rotation of the meshing gears 45 and 46 produces a torque tending to twist the gear box 43 as a whole, and this torque is resisted by the tube 9. The gear 45 is rigid with a sleeve 45a (see Figure 2a) slidably mounted on the shaft 32 and keyed to said shaft by a key 45b engaging in groove 32a and can be slid out of engagement with the gear 46 by movement of the handle 47 which co-operates with the crank 48 and forked arm 49 to slide the gear 45. In this way drive can be disconnected from the spindle 44 when desired. It will be seen that the gear box 43 will move with the ram 17, the driving shaft 32 sliding similarly within the shaft 29') while still maintaining the drive to the spindle 44. During drilling when the ram 17 has been extended to the maximum the feed of the ram is reversed and drive to the spindle 44 can be disconnected during this reverse movement.

The end plate 36 has a threaded bore to receive a water line attachment whereby water can be supplied to the drill when drilling with a rod adaptor through the interior of tube 33, ram 17 and spindle 44, a sealing gland being fitted at the rear end of spindle 44 to prevent the entry of water into the gear box 43.

The drill is mounted on a conventional rock drill column and clamped by means of a coned hinge plate 51 hinged to either one of two lugs 52 on the main casing 10 and secured by a clamping bolt 53' By having two lugs 52 the hinge plate can be fitted on either side of the drill. The drill can be swung down out of line with a drill hole merely by releasing the clamping bolt 53. The arrangement is thus such that the line of the drill rod is brought as close as possible to the centre of the mounting column.

The hydraulic unit will now be described in more detail. The pump 13 is of known kind and is mounted on the front of the control block and lies partly within the expansible oil reservoir 14. The front end of the reservoir 14 is closed by a plate 55 and a spring 56 bears against the plate 55 to ensure that there is no air space within the reservoir 14 so that the inlet of the pump 13 remains immersed irrespective of the attitude or position of the drill (that is, whether drilling is taking place vertically, horizontally, or at any angle) provided that there is a minimum quantity of oil in the system. An indicator rod 57 attached to the plate 55 shows on the outside of the casing the amount of oil in the reservoir 14. The rod 57 has one end secured to plate 55 and its other end 3 is provided with a small block 57a arranged in a groove 57b in the casing (Fig. 2b). The movement of the block 57a corresponds with the movement of plate 55 and accordingly the position of the block against a suitable graduated scale on the casing will indicate the amount of oil in the reservoir. The reservoir 14 can be filled by removing the threaded plug 58 (see Figure 3). This can be seen in Figure 3, which is a diagrammatic representation of the feed control system, wherein the large diameter bore 58a at the top of block 15 communicates with the reservoir 14 which (as indicated by the chain-dotted lines) extends across the whole left-hand face of block 15 as viewed in Figure 3. Thus, when plug 58 is removed oil can be poured through the bore 58ainto reservoir 14. 7

Referring now to Figure 3, the pump 13 delivers oil under pressure through a passage 101 to a port 59 which is connected by passage 102 to a reversing valve 60-, passage 103 to a pressure control valve 61 and passage 104 to a cut-out valve 62.

Dealing first with the reversing valve 60-, this controls the direction of feed, i. e. forward or reverse, by determining to which end of the ram cylinder oil is admitted. In Figure 3, this valve is shown in the reverse feeding position and oil passes from passage 102 to pipe line 42 serving the front end of the ram cylinder via annular port e 63 and inclined passage 105 invalve 60, port 117 in sleeve 116 and passage 106. Oil is returned from the rear end of the ram cylinder to the reservoir 14 via pipe line 141, passage 197, port 118 in sleeve 116, inclined passage 108 and axial passage 109 in the valve 60 and passage 64 which opens directly into the reservoir 14. By turning valve 60 through 180 forward feed is provided, since passage 102 is then connected by passage 105 and port 118 to passage 107 and passage 106 is connected by port 117 and passages 108 and 109 to passage 64.

It should be noted that as the reversing valve 60 is turned towards the forward feeding position it takes up an intermediate position inwhich port 117 is connected to passage 109 by way of a small port 110 in valve 60 and a spring loaded ball 111. 117 and 118, which are transverse bores in sleeve 116,- have diameters greater than those of passages 105 and 108 and port 110, and that it is so arranged that passage 105 is in communication with port118 whether valve 60 is in the forward feeding position or inthe intermediate position. When feeding downwardly a heavy string of drill rods, the weight of the rods might in certain circumstances pull the ram forward at a rate greater than that 7 corresponding to the rate of delivery of pressure oil to the placing the valve 60 in the intermediate positionmentioned above, the return flow of oil is restricted and the operator is. enabled tornaintain control of the movement. The pressure control valve 61 has a plunger. 65 which lifts when the pressure exceeds a predetermined value: determined by the pressure of spring 66. and thereby bypasses oil to the reservoir 14 through the passage:67. The setting of the valve is adjusted by movement of the knob-- 68 which varies the spring pressure, thereby enabling the pressure of the oil fed to the ram cylinder to be continuously varied over a Wide range, the pressure being automatically maintained at the. value for which the: valve.61' is'set.

The cut-out valve 62 serves two-purposes, it automatically cuts out feeding of the drill when apredetennined limit of travel is reached in either the forward or reverse directions; it also prevents drill. feedwhen the machine isbeing started up or closed down i. e. when the drillisrotating-at low R. P. M. The valve 62' operates; inconjunction with an air valve inthe form. of: a cut out actuating plunger 69. The plunger 69 is mounted in2the endcover 30 and its end isurged by spring 74- against the torque resistor tube 9 which has two apertures 70 (only It should be noted that ports one shown in Figure 3) located along the tube 9 at positions corresponding to the extremes of travel of the tube 9. Compressed air from the pneumatic motor inlet 23 is fed to the passage 71 and, with the air valve 25 open and the torque resistor tube 9 at an intermediate position (as shown), the air passes through port 72 in the plunger 69 and hence via passage 73 tothe cut out valve 62.

The body of valve 62' is held to the left (as shown in Figure 3-) by the compressed air from passage 73 and engages a flange 112a on a plunger 112 which holds a ball 75 on its seating. A spring 113 is arranged to act between the valve body 62 and plunger 112, but itwill be noted that in the valve position shownit has no effect in holding the ball 75 on its seating. The air pressure in passage 73 may be below a predetermined value either because the pneumatic motor is being started up or stopped, or because a. predetermined limit of travel has been reached and plunger 69 enters an aperture 70 thereby cut-.

ting off the air supply to valve 62. When the air pressure on the valve body 62 drops below this predetermined value, the body 62 moves to the right under the influence of spring 113 (assuming for the moment that ball 75 and plunger 112 remain in the position shown). However, plunger 112 is now free to move to the right since flange 112a no longer engages valve body 62, and therefore only the pressure exerted by spring 113 can hold plunger 112 to the left and ball 75 on its seating. It is arranged that this spring pressure is such that when the cut out valve is in its right-hand position, the oil pressure can only attain a predetermined value less than that necessary for normal ram feed. This value is however sufficient to sustain the weight of drill rods when drilling upwardly. Any tendency for the oil pressure to rise above the predetermined value results'in the ball 75 being lifted from its seating so that passage 104 is put into communication with passage 76 and oil is returned directly to the reservoir 14. The valve 62 is provided with an annular port 114 communicating through passage 115 with the atmosphere, thereby providing a relief outlet for compressed air which might otherwise penetrate frompassage 7-3 into the hydraulic system.

The invention claimed is:

l. A rock drill comprising a casing, a hollow shaft rotatably'mounted in said casing, a compressed air motor for rotating said shaft, a drill bit supportingmember mounted for longitudinal movement relative to said casing, a drive shaft disposed within said hollow shaft for rotation therewith and longitudinal movement relative thereto, meansmovable with said bit supporting member for drivingly connecting said drive shaft to said bit supportingmember, a piston connected to said bit supporting member whereby longitudinal movement of said piston produces corresponding movement of said bit supporting member, and a closed circuit hydraulic system including a pump driven by said motor and means for connecting said pump selectively to either side of the piston to supply hydraulic fluid to one or the other side of said piston for producing longitudinal movement thereof.

2. A rock drill comprising a casing, a compressed air motor supported by said casing, a drill bit supporting member arranged for longitudinal movement relative to said. casing, means for drivingly connecting said motor to said' drill bit supporting member to rotate the latter irrespective of its position relative to said ca'sing,.an outer tube supported bysaid casing, an inner tube supported coaxially within-and spacedfrom saidouter' tube, a piston disposed in the space between said tubes and arranged slidingly to engage said tubes in afluid tight manner, a hollow ram also disposed within said' space and attachedto said piston and bit'supporting member to transmit lon gitudinal movement of said piston to said drill bit supporting'mernber, anda closed circuit hydraulic system including-a pump driven by said motor and a'dapted'to supply'hydraulic fluid to on'eor the other side of said piston toproduce longitudinal movement thereof.

3. A rock drill comprising a body portion, a compressed air motor supported by said body portion, an bydraulic pump also supported by said body portion, a shaft rotatably mounted in said body portion and arranged to transmit drive from said motor to said pump, a gear box mounted for longitudinal movement relative to said body portion, a hollow drill bit supporting member rotatably supported by said gear box, a drive shaft arranged to rotate with said first mentioned shaft and to move longitudinally relative thereto, means for rotatably connecting said drive shaft to said drill bit supporting member, inner and outer tubes forming an annular space between them, an annular piston disposed within said annular space for longitudinal movement therein, a hollow ram slidable on said inner tube, the interior of said ram communicating with the interior of said hollow drill bit supporting member and being secured to said piston and gear box for transmitting longitudinal movement thereof to said gear box, the inner wall of said inner tube enclosing a space which communicates with the interior of said ram and is accordingly available for conveying water to or dust from the work face, and a closed circuit hydraulic system including said pump which is adapted to supply fluid into said annular space to one or the other side of said piston for producing longitudinal movement thereof.

4. A rock drill comprising a body portion having a first bore, a second bore, a third bore and a fourth bore, said bores extending parallel to one another, a compressed air motor disposed within said first bore, an hydraulic pump also disposed within said first bore, a hollow shaft rotatably mounted in said second bore and adapted to be rotated by said motor to drive said pump, a double-walled hollow cylinder secured in said third bore, an annular piston disposed in the space between the double walls of said cylinder so as to slide in a fluid-tight manner in said space, a hollow ram also disposed in said space and having a front end and a rear end, the rear end of said ram being secured to said piston, a gear box secured to the front end of said ram, a torque resistor tube slidably mounted in said fourth bore and having a front end secured to said gear box, a drive shaft mounted in said shaft for rotation therewith and longitudinal sliding movement relative thereto, said drive shaft having a front end rotatably mounted in said gear box, a gear mounted on said front end of said drive shaft for rotation therewith, a hollow chuck-rotating spindle rotatably mounted in said gear box, the interior of which spindle communicates through said hollow ram with the interior of said double-walled hollow cylinder, a gear fast on said spindle, means for moving said drive shaft gear into and out of mesh with said spindle gear and a closed circuit hydraulic system for feeding said gear box towards and away from said body portion and including said pump and said space between the double walls of said cylinder together with a flexible hydraulic fluid reservoir in said first bore adapted to accommodate itself to the volume of fluid therein, pipe lines through which said fluid is supplied by said pump into said space on one side of said piston and through which fluid returns from said space on the other side of said piston to said reservoir, a reversing valve for determining to which side of said piston said fluid is supplied, a pressure control valve adapted to by-pass fluid direct from said pump to said reservoir when the fluid pressure exceeds a predetermined value, cut-out valve means which operate to reduce the fluid pressure to a value below that required for ram feed, means for supplying to said cut-out valve means air from the air inlet to said compressed air motor, said cut-out means being in operative or inoperative position according to whether the pressure of said air is below or above respectively a predetermined value, and means for cutting off said air supply to said cut-out valve means when the ram reaches either end of its travel.

5. A rock drill comprising a body portion adapted to be secured to a supporting stand or the like, a compressed air motor mounted on the body portion, a drill bit supporting member, means mounting said bit supporting member on the body portion for rotation about an axis and for movement along such axis, a piston, means slidably mounting the piston in the body portion, means operatively connecting the piston to the bit supporting member for moving the member along its axis of rotation when the piston slides in the body portion, means operatively connecting the air motor to the bit supporting member to rotate said member, a closed hydraulic circuit, including a pump, means operatively connecting the air motor to the pump to drive the pump, said circuit including connections from the pump to each side of the piston, and means to control the flow of fluid in such connections to move said piston and supporting member in either direction.

6. In a drill according to claim 5, said circuit including means forming a hydraulic fluid reservoir in said body portion, said reservoir forming means including a movable Wall exposed to pressure on the outside whereby movement of said wall decreases the volume of the reservoir as fluid is pumped therefrom, and a connection from said reservoir to the inlet of said pump.

7. In a drill according to claim 6, said means connecting the motor to the drill supporting member including a shaft, means mounting the shaft in the body portion for sliding movement parallel to the direction of sliding movement of the piston, and means operatively connecting said shaft to said motor and to said bit supporting member.

8. In a drill according to claim 5, means responsive to the sliding movement of the drill bit supporting member and connected to said hydraulic circuit to reduce the pressure in said circuit when said bit supporting member reaches the limits of its stroke.

9. In a drill as claimed in claim 8, said pressure reducing means including a cut-out valve in said hydraulic circuit responsive to a drop in air pressure thereon below a predetermined value to reduce the pressure in the hydraulic circuit, means normally maintaining a pressure above said predetermined pressure on said cut-out valve, said last means including a line leading to said cut-out valve, means to supply air under pressure to said line, a normally open control valve in said line, and means responsive to the travel of the bit supporting member to either of its limits of travel to close said control valve.

10. In a drill according to claim 5, said control means including a manual valve in said circuit for selectively directing fluid from said pump to one or the other of the pump-piston connections.

11. In a drill as claimed in claim 10, pressure control means in said circuit to maintain the pressure therein below a predetermined value.

12. In a drill according to claim 11, means responsive to the sliding movement of the drill bit supporting member and connected to said hydraulic circuit to reduce the pressure in said circuit when said bit supporting member reaches the limits of its stroke.

13. In a drill according to claim 5, said control means including a manual valve in said circuit for selectively directing fluid from said pump to one or the other of the pump-piston connections, and means responsive to the sliding movement of the drill bit supporting member and connected to said hydraulic circuit to reduce the pressure in said circuit when said bit supporting member reaches the limits of its stroke.

14. In a drill as claimed in claim 13, said pressure reducing means including a cut-out valve in said hydraulic circuit responsive to a drop in air pressure thereon below a predetermined value to reduce the pressure in the hydraulic circuit, means normally maintaining a pressure above said predetermined pressure on said cut-out valve, said last means including a line leading to said cut-out valve, means to supply air under pressure to said line, a normally open control valve in said line, and means 

